A resistance-based temperature sensor, or resistance temperature detector (RTD), can be used in a number of applications to measure the operating temperature of an environment or system based on a sensed change in resistance in one or more wires incorporated into the sensor. When connected to a stator, such as those used in motors, generators and auxiliary equipment, an RTD can be used to detect temperatures in stator windings, as well as the temperatures of associated air and gas streams.
To connect an RTD to a stator, the RTD is typically installed inside the stator core. This may be accomplished by installing the RTD completely within an opening or slot formed between the stator windings or coils, with only the sensor's associated insulated wires protruding past an edge of the stator core. Typically, this type of RTD includes a thin, rigid body (e.g. a fiberglass body) for housing the sensing portion. Relatively large electrical leads forming the connection to the sensing portion generally do not fit inside the fiberglass body. Accordingly, these arrangements require the formation of a “lead step”, which may comprise a deposit of fiberglass material on the lead wire ends where they join the fiberglass body. This lead step makes the RTD installation process and its positioning inside a motor or generator more difficult than other applications, as well as susceptible to damage during motor or generator manufacturing.
Further, RTDs used in stator and other space-constrained applications often exhibit tensile failures during installation and manufacturing, as RTDs are friction fit, for example, within the stator windings. The cause of these failures can be linked to stress on the RTD sensing wire resulting from the installation process, which can include pressure, blows with rubber mallets, and bending of the lead end/lead step area of the RTD at the edge of the stator core.
Accordingly, more robust stator winding temperature sensors are desired.